The unidentified stunt driver appeared to have lost control of her motorcycle and went through a window of the downtown Shaw Tower on Monday, according to witnesses.

Nathan Kramchynski works in the same building where the accident happened, and said he had been watching rehearsals of the stunt earlier.

The stunt woman had been riding the motorcycle down a set of stairs at the Vancouver Convention Centre, stopping at the street. On the last attempt, he said the stunt woman crossed the street and swerved to avoid pedestrians.

"She lost control really quickly. It happened in a split second,'' he said. "She was going full throttle and then there's a building there.''

THE CANADIAN PRESS
A police officer photographs a motorcycle after a stunt driver working on the movie "Deadpool 2" died after a crash on set, in Vancouver on Aug. 14, 2017.

THE CANADIAN PRESS
A police officer takes photographs after a female stunt driver died after a crash on the "Deadpool 2" set in Vancouver on Aug. 14, 2017.

THE CANADIAN PRESS
Ramps for a motorcycle stunt are seen on the steps outside the Vancouver Convention Centre while police officers investigate after a stunt driver working on the movie "Deadpool 2" died after a crash on set in Vancouver on Aug. 14, 2017.

Sharmina Kermalli said she had just walked inside a Starbucks next door when the sound of a loud crash prompted her to run outside.

The stunt driver was laying on the ground, she said, adding that pieces of glass were falling on her.

"I was thinking, what if I was just five seconds (later),'' Kermalli said.

The BC Coroners Services and WorkSafeBC are both investigating, police said in a release.

The Marvel superhero sequel stars Vancouver-born Reynolds and set locations have been spotted across the city throughout the summer.